A U.S. federal judge allowed a class-action suit against Google to proceed, saying the company's terms of service are unclear when describing how it scans Gmail content in order to deliver advertisements.

Google had filed a motion to dismiss the suit, which alleges that the company intercepted and read email while in transit in order to deliver advertisements and create user profiles and models since 2008. The plaintiffs alleged the company violated federal and state wiretapping laws.

The suit, which is being heard in U.S. District Court for the Northern District of California, further contends non-Gmail users who sent email to Gmail users were also subject to illegal interception.

In her ruling Thursday, U.S. District Judge Lucy H. Koh wrote that Google's terms of service and privacy policies do not explicitly say that the company intercepts users' email to create user profiles or deliver targeted advertising.

Although Google revised its terms of service and privacy policy in 2012, Koh wrote "that a reasonable Gmail user who read the Privacy Policies would not have necessarily understood that her emails were being intercepted to create user profiles or to provide targeted advertisements."

Google said in a statement it was disappointed with the decision and is considering its options. "Automated scanning lets us provide Gmail users with security and spam protection, as well as great features like Priority Inbox."

Google, which had filed a motion to dismiss, maintains that the automated scanning is fully disclosed to Gmail users and that features such as search and filtering would not be possible without it.

Past court rulings have also held that all email users imply consent to automated processing since email couldn't be sent otherwise, Google argued in the motion.

Koh also rejected Google's contention that non-Gmail users gave their implied consent to scanning of their communications.

"Google has cited no case that stands for the proposition that users who send emails impliedly consent to interceptions and use of their communications by third parties other than the intended recipient of the email," Koh wrote.

Consumer Watchdog, a nonprofit consumer advocate group based in Washington, D.C., called Koh's ruling a "tremendous victory for online privacy."

"The court rightly rejected Google's tortured logic that you have to accept intrusions of privacy if you want to send email," said John M. Simpson, Consumer Watchdog's privacy project director, in a news release. "Companies like Google can't simply do whatever they want with our data and emails."